Another advantage of this method is that the frequency of slave laser can be dynamically tuned, following the master laser frequency. Fig. REF  shows the wavelength (top) of the slave laser and the corresponding PID output voltage (bottom) from the feedback controller when the master laser linearly scans over 1 GHz. The change of the injection locking point induced by the master laser is readily compensated by the active feedback in contrast to the passive injection locking. Our results suggest that the demonstrated active feedback method is useful for not only the frequency stabilization, but also dynamically tracking the injection locking states. This feature would be critical in applications where the slave laser frequency is also required to vary, for example, coherent light detection and ranging (LIDAR) for range detection [1]}. The feedback bandwidth of our locking scheme is mainly determined by the current controller (Thorlabs, LDC202C, 100 kHz) of the slave laser. We have evaluated the feedback bandwidth by modulating the current of the master laser.
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